Cutaneous Fungal Microflora of Healthy Squamate Reptiles and Prevalence of the Chrysosporium Anamorph of Nannizziopsis vriesii
A survey was conducted to investigate the presence of a fungus, the Chrysosporium anamorph of Nannizziopsis vriesii, on the skin of healthy squamate reptiles. Skin was collected as aseptically as possible from actively shedding animals or from freshly shed exuvia. Initial results of culture from skin samples of 31 different lizards and 48 snakes, belonging to 29 zoologic and veterinary institutions, demonstrate a varied cutaneous fungal microflora. Fungi belonging to 41 genera were identified from these 79 reptiles. Aspergillus spp., Penicillium spp., and Paecilomyces lilacinus were most frequently retrieved; however, N. vriesii was not recovered from any of these reptiles. Nannizziopsis vriesii, increasingly incriminated in fungal disease in reptiles, does not appear to be a common constituent of the microflora of healthy reptiles. This study, therefore, provides some basis to suggest that mycosis is not an infrequent outcome of exposure of reptiles to N. vriesii spores, at least under certain conditions.
The fungus Nannizziopsis vriesii has been implicated in several outbreaks of skin disease in reptiles.1-3 In documented outbreaks, animals were wild-caught specimens and the stress of capture and shipping likely was contributory to the onset of mycosis, yet the source of the fungus was never clearly identified.1,2 Whether N. vriesii is a common environmental fungus found in soil or in cage substrate, or is part of the normal reptile skin microflora opportunistically causing disease in stressed animals, or whether it is a true transmissible or contagious pathogen is presently unknown. The main objective was to determine the prevalence of N. vriesii and other fungi on the skin of healthy captive reptiles. Initial colonies of N. vriesii are white and powdery and the hyphae produce small club-shaped conidia and arthroconidia. We paid particular attention to the presence of Chrysosporium species and to any dermatophyte-like fungi, but other fungi were determined at least to genus and often to species.
In October 2000, sample submission request packages were forwarded to institutions in the United States and Canada. Each solicited institution was asked to submit duplicate 2.5x2.5-cm samples of shed skin from three different individual squamate reptiles. These were to be collected as aseptically as possible from an actively shedding lizard or snake, or from a freshly shed snake exuvia. Samples were sent to two universities for culturing. Skin samples were cut in small sections, and these were plated onto Mycosel agar (Becton Dickinson, and Company, Cockeysville, MD, USA) containing chloramphenicol (0.0005%), and cycloheximide (0.04%). Fungi were identified on the basis of morphology and growth pattern of colonies and on microscopic observation of conidiation and fruiting bodies.
To date, over 35 institutions have participated in the study. Preliminary results presented here are based on skin samples from 31 lizards and 48 snakes. From the 79 samples (158 culture plates), 451 fungi were keyed to a total of 41 genera. Twenty Chrysosporium isolates were identified from 19 of the 79 reptiles (24%). Sixteen of these were C. zonatum, three were typical of the Chrysosporium anamorph of Aphanoascus fulvescens, and one was C. evolceanui. None of the Chrysosporium isolates met the N. vriesii-anamorph criteria. Initial results of this survey strongly suggest that N. vriesii is not a common constituent of the cutaneous microflora of healthy reptiles.
The most prevalent fungal genera were Aspergillus, Penicillium, and Paecilomyces. Penicillium was isolated from 61 (77%), Aspergillus from 56 (71%) and Paecilomyces from 28 (35%) of the 79 reptiles. Remaining isolates belonged to 25 other genera. We cultured an average of 4.4 different genera of fungi per reptile (range of 0 to 15), often with more than one species per genus of fungus (e.g., two species of Penicillium or Aspergillus). Whether an animal was arboreal, terrestrial or fossorial did not seem to be predictor of the number or types of isolates cultured from its skin. There was a weak but discernible trend for reptile skins from the same institution to yield similar microfungi.
Since it has now been implicated in several outbreaks of dermatomycosis in reptiles, and since data provided here suggest a low prevalence in the environment of captive reptiles, it appears logical to infer that N. vriesii carries a definite pathogenic potential for reptiles exposed to its spores, and infection needs only be triggered by a specific combination of environmental and host factors, such as faulty husbandry or stress. Further studies are necessary to determine the conditions and factors that govern infection of reptiles by this fungus.
This survey was funded in part by the Association of Reptilian and Amphibian Veterinarians, the Companion Animal Trust Fund, School of Veterinary Medicine of the University of Wisconsin, and the University of Alberta Small Faculties Fund Support for the Advancement of Scholarship. The authors wish to thank the following collaborating institutions: The Wildlife Care Center, FL, Barbertown Veterinary Clinic, OH, Kansas State University College of Veterinary Medicine, Roger Williams Park Zoo, RI, Long Beach Aquarium of the Pacific, CA, Steinhart Aquarium, CA, Brevard Zoo, FL, Staten Island Zoo, NY, Central Florida Zoo, FL, John Ball Zoo, MI, Six Flags Marine World, CA, Potawatomi Zoo, IN, Lakeside Animal Hospital, WI, Oregon Zoo, Virginia Zoological Park VA, Tautphaus Park Zoo, ID, Zoo America, PA, Ben Lomond Animal Clinic, UT, Glastonbury Veterinary Hospital, CT, Dakota Zoo, ND, Topeka Zoological Park, KS, Burnet Park Zoo, NY, Westover Animal Clinic, MA, Bergen County Zoological Park, NJ, Micke Grove Zoo, CA, Oglebay’s Good Zoo, WV, St-Augustine Alligator Farm, FL, San Diego Zoo, CA, and the Audubon Zoo, LA.
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2. Paré, J.A., L. Sigler, D.B. Hunter, R.C. Summerbell, D.A. Smith, and K.L. Machin. 1997. Cutaneous mycoses in chameleons caused by the Chrysosporium anamorph of Nannizziopsis vriesii (Apinis) Currah. J. Zoo Wildl. Med. 28:443–453.
3. Sigler, L. and A.D. Thomas. 2000. Nannizziopsis vriesii causing cutaneous infections in Australian saltwater crocodiles. ASM Abstr. Z-6.